Serotonin (5-HT) neurotransmission plays an important role in numerous physiological processes both in health and in psychiatric disorders. As an example, 5-HT has been implicated in the regulation of feeding behavior. It is believed that 5-HT induces a feeling of fullness or satiety so that eating stops earlier and fewer calories are consumed. As the 5-HT2C receptor is expressed in high density in the brain (notably in the limbic structures, extrapyramidal pathways, thalamus and hypothalamus i.e. PVN and DMH, and predominantly in the choroid plexus) and is expressed in low density or is absent in peripheral tissues, development of a selective 5-HT2C receptor agonist is desirable, having improved efficacy and safety over other anti-obesity agents and related drugs.
The compound, (R)-8-chloro-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine, whose structure is shown below in Formula I, belongs to a class of 5-HT2C agonists that are useful in the treatment of a number of 5-HT2C-related diseases and disorders, such as those mentioned above. Preparation and characterization of this compound are described in WO 2003/086306, which is incorporated herein by reference in its entirety. Preparation and characterization of the hydrochloric acid salt of this compound is also described in International Application No. PCT/US04/19279 which is incorporated herein by reference in its entirety. Because drug compounds having, for example, improved stability, solubility, shelf life, and in vivo pharmacology, are consistently sought, there is an ongoing need for new or purer salts, hydrates, solvates, and polymorphic crystalline forms of existing drug molecules. The crystalline forms of (R)-8-chloro-1-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride described herein help meet this and other needs.
